1. Technical Field
The present invention relates to a tube for a heat exchanger formed by rolling an aluminum material to provide a partition for dividing a passage, its production method and a heat exchanger using the tube.
2. Background Art
Conventionally, as a tube for a heat exchanger, there is known a flat tube which is formed by rolling an aluminum material.
For example, a heat exchanger used for vehicles may be a combination of at least two heat exchangers having different functions.
Among the tubes used for such heat exchangers, the tube described in, for example, Japanese Patent Laid-Open Publication No. 6-123571 or No. 7-41331, is formed by having a partition which is formed to have an approximately xcex8-shape cross section by bending an aluminum material in multiple stages by rolling, and forming a plurality of passages in the tube by adhering the partition and a wall facing the partition by brazing in an oven.
This type of tube for a heat exchanger is formed with the partitions in the tube even though the number of step is relatively few, so that recently it is used as a tube for a heat exchanger used for a refrigeration cycle for cars.
The heat exchangers are becoming smaller in size with improvement of their performance. Therefore, an aluminum improvement of their performance. Therefore, an aluminum material having a less thickness of about 0.2 mm is being used for the tubes for the heat exchangers. The size of tube being used is made very small and thin with dimensions of a width of about 15 mm and a height of about 1.5 mm.
A heat exchanger tube to be used for a compact heat exchanger is required to have an accuracy for the dimensional control when it is formed by rolling. Meanwhile, the formed tube has dimensional unevenness concentrated on the neighborhood of the portion corresponding to the ends of the tube material in the final sectional shape.
For example, when the tube is formed, a partition part is formed at ends of the tube material and the partition parts formed at both ends of the material are joined to form a partition. When the partition parts are formed at the ends of the tube material where unevenness tends to occur while the tube is being formed, a gap or the like is formed on the tube, and the dimensional control may become insufficient. And, brazing may become defective depending on a degree of unevenness produced. The tube for a heat exchanger which has a defective brazing or the like has a defective pressure strength, or the right and left passages in the tube become non-uniform. Therefore, there is a problem that a defective bypass is produced or leakage to outside occurs.
Therefore, it is an object of the present invention to provide a tube for a heat exchanger which is produced while eliminating unevenness which could be caused in machining to form the tube, its production method and a heat exchanger.
The invention described in claim 1 is a heat exchanger formed by rolling a flat tube material, forming tubes having a passage with at least one end open, stacking the tubes with fins interposed between adjacent tubes, disposing tanks on the side of the passage openings of the tubes, joining the tanks and the tubes to appropriately communicate the tubes and the tanks, wherein the tubes are provided with a first flat section, first erected sections which are erected at about right angles from both ends of the first flat section, and a second flat section which is continuous from the first erected sections and substantially parallel to the first flat section; partition parts are formed on the second flat section by bending the ends of the second flat section; and the partition parts are contacted with the first flat section to establish a partition for dividing the passage of the tubes.
The invention described in claim 2 is a tube for a heat exchanger which is formed by rolling a flat tube material and has a passage with at least one end open, wherein the tube is provided with a first flat section, first erected sections which are erected at about right angles from both ends of the first flat section, a second flat section which is continuous from the first erected sections and substantially parallel to the first flat section, and a partition for dividing a tube passage; and the partition is provided with partition parts formed by bending the tube material and an extra section for absorbing deformation, which is produced when the tube is formed, as much as possible.
The invention described in claim 3 is the tube for a heat exchanger according to claim 2, wherein the extra section has a shape to cut into the first flat section.
The invention described in claim 4 is the tube for a heat exchanger according to claim 2 or 3, wherein the extra section has a shape to cut into the second flat section.
The tube used for a heat exchanger of the present invention is provided with the partition in the passage of the tube for the heat exchanger even when it is formed of a thin material for use in a compact heat exchanger, so that a required pressure strength can be assured.
And, the partition of the tube for a heat exchanger absorbs unevenness, which is produced while machining, by the extra section as much as possible. As a result, the formed tube for the heat exchanger is prevented from having a defective brazing and can hold the required pressure strength. The tube for the heat exchanger has the passages equally divided by the partition and can prevent a defective passage or the like in the tube. Therefore, it becomes possible to produce a quality heat exchanger.
And, when the extra section is formed in such a way to cut into the first flat section, the contacted portion of the partition parts and the first flat section becomes wide, the brazing property is improved, and the partition parts and the first flat section are joined with good watertightness.
When the extra section is formed so to cut into the second flat section, the partition parts and the second flat section are joined with good watertightness.
The invention described in claim 5 is the tube for a heat exchanger according to claim 2, wherein the tube material has a size exceeding two times a vertical size of the partition in addition to a predetermined material size for forming the tube for a heat exchanger; and the partition has partition parts which are formed to protrude from the second flat section by bending and joining the ends of the tube material to form overlaid portions and bending a predetermined point of the overlaid portions at about right angles and extra sections which are joined along the second flat section.
When the extra section to be joined along the second flat section is provided according to the present invention, the tube can keep the precision of the tube shape because a deformation caused when the tube is being produced can be absorbed as much as possible by the extra section by the effect of sizing performed after or in the process of forming the tube.
The tube of the present invention has an improved pressure strength by forming the overlaid portion which has the ends of the tube material bent and joined, forming the partition parts by bending the overlaid portion, and mutually contacting the partition parts to form the partition. Therefore, the partition has a state that the tube material is overlaid four times.
The invention described in claim 6 is a method of producing a tube for a heat exchanger which is formed by rolling a flat tube material and provided with a partition for dividing a passage, wherein the tube material has a size exceeding two times a vertical size of the partition in addition to a predetermined material size for forming the tube; the method comprising a first step to form an overlaid portion by bending a predetermined portion of the ends of the tube material to substantially 180 degrees and joining; a second step to form partition parts by bending a predetermined portion of the overlaid portion or a predetermined portion of the tube material to substantially 90 degrees and extra sections for absorbing deformation, which is caused when the tube is formed, as much as possible; and a third step to form the tube by contacting the protruded ends of the partition parts to the first flat section.
The invention described in claim 7 forms the extra sections which cut into the first flat section in the first or second step of claim 6.
According to the method of producing the tube for a heat exchanger of the present invention, the contact portion between the partition parts and the first flat section becomes wide when the tube is formed because the extra section which cuts into the first flat section is formed, the brazing property is improved, and the partition parts and the first flat section are joined with good watertightness to form the tube.
The invention described in claim 8 forms the extra sections which cut into the second flat section in the first or second step of claim 6 or 7.
According to the method of producing the tube for a heat exchanger of the present invention, the partition parts and the second flat section do not cause a gap and joined with good watertightness when the tube is formed because the extra section which cuts into the second flat section is formed.
The invention described in claim 9 is the invention according to claim 6, wherein the first step includes a step to form the first bending section which becomes a bending fulcrum of the overlaid portion, and a step to form the second bending section which has an inner angle larger than that of the first bending section.
The method of producing the tube for a heat exchanger of the present invention decreases the load applied to the first bending section and forms the overlaid section while keeping precision without causing displacement on the first bending section when the second bending section which has the inner angle larger than the inner angle of the first bending section is formed at the leading end of the first bending section which is the bending fulcrum and the overlaid portion which has the ends of the tube material bent and joined is formed.
The invention described in claim 10 is the invention according to any one of claims 6 to 9, wherein the third step is provided with a step to correct unevenness in precision when the tube is formed by deforming unevenness.
According to the method of producing the tube for a heat exchanger of the present invention, unevenness in precision caused when the tube is formed is absorbed for correction by the extra section or the like, and a quality product with precision can be formed.